RE: [CAD_CAM_EDM_DRO] Z-Axis Knee Woes

I have one of those 600 oz in motors on my 8X36 knee mill. I am using a
2.5/1 ratio timing pulley. I would recommend a 3/1 ratio. I can raise
and lower my knee with a #105 mill vice on it all day long without the
motor getting warm and at good speed. The G320's never fault except when
I run the knee into the stops. (AAAARRRGGGHH I hate it when I do that)
The trick is make sure you have a 3/1 and I also put a lower encoder
count onto that motor so that I would not have a larger count on the Z
axis. I ended up using a 60X037 pulley on the handshaft and a 24XL037
pulley on the motor. These are not that expensive! But I would recommend
a full 3/1 ratio and possibly a 4/1.
Dan



-----Original Message-----
From: jbordens <jake@...> [mailto:jake@...]
Sent: Monday, January 13, 2003 4:59 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Z-Axis Knee Woes


Hi folks. I'm retrofitting a G3102 Grizzly Knee Mill, a smaller type
mill somewhere bigger than a drill mill, but smaller than a full
bridgeport.

I just finished my Z-axis, after success with X and Y. I decided to
motorize the knee for various reasons. I'm using Camtronics 600-in-oz
motors and a 2:1 ratio on the pulleys.

The knee is driven by a shaft that is at 90-degrees to a jackscrew.
The shaft is connected to the jackscrew via a set of helical spur gears.

Here are my problems:

(1) the motors aren't powerful enough, apparently, to raise the knee.
They stall and eventually cause my geckos to fault. I'm pretty sure I
have the "limit" set to Max on the geckos.

(2) when lowering the knee, the motor turns and every now again there's
a 'thump' from the mill, as if the knee is not lowering smoothly, but in
little increments.


I guess I have two options:

(a) go to a higher ratio, but 2:1 was the most practical. 3:1 is
possible but expensive, and anything more is really not possible due to
pulley size constraints.

(b) counterweight the knee. I think this is complicated and probably
not a good idea.

In either case I'm not sure it would solve problem #2. I'm currently at
a loss on how to proceed. Any suggestions are greatly apprecaited.

Thanks,
Jake


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